Reports Spotlight Free-Electron Lasers (Times-Dispatch)

Reports Spotlight Free-Electron Lasers

By A.J. Hostetler, Times-DispatchAugust 20, 1998

WILLIAMSBURG -- George Neil's promise to spring for a case of fine California wine is safe for another year.

The physicist at the Thomas Jefferson National Accelerator Facility in Newport News had promised the wine to his colleagues at an international conference in 1995. The prize would go to the team whose free electron laser put out 1 kilowatt of power for a full second.

Free electron lasers use the electron to produce one of the most powerful and controllable light sources ever. Fewer than two dozen FELs have been built since it was invented in 1977. Recent technological advances and the promise of a powerful and controllable light source are increasing that number. A handful are under construction, and five came on-line in the past year alone, including one at the Jefferson Lab.

On Monday, physicists at the conference gave reports on "first light" at the new FELs. Some, such as one in the Netherlands, were quite powerful for micro-fractions of a second. The Jefferson Lab reported hitting, and sustaining, 311 watts for hours, a world record for its type of laser.

Neil, deputy program manager of the Jefferson FEL program, said he'd like to give the wine away.

"It's now a two-horse race," he said, between FOM and his group at Jefferson, which hopes to reach 1 kilowatt sometime this fall after scientists spend time putting the laser through its paces to learn its limitations.

But power isn't everything. Just as a sports car is about more than the horsepower of its engine, FELs are also about control and performance.

A laser beam is a concentrated beam of light confined to a single wavelength. FEL researchers have "tuned" their lasers to different wavelengths. Some, including those at the Jefferson Lab, work with a wavelength in the infrared end of the spectrum, while others work with the shorter ultraviolet wavelengths.

A team of researchers from Vanderbilt University presented reports on its use of an FEL for medical applications, particularly surgery. Although Vanderbilt once held the record for the most powerful infrared FEL, 11 watts, it typically runs at about half that because surgeons don't want or need power to burn away tissue.

Charles Brau, the former head of Vanderbilt's FEL team, said the university plans to use its laser later this year on its first human patient, to try to destroy an otherwise untreatable brain tumor.

Duke University physicists also are studying medical applications and basic science with its UV laser. Today, Vladimir Litvinenko's group was to report on the success of its FEL, which has gone the deepest into UV territory, at 217 nanometers, near the range where the laser could be used in eye surgery. The team hopes eventually to hit .4 nanometers, smaller than the size of a single atom, in the gamma-ray range.